#include <stdio.h>
#include <math.h>

void f()
{
  int a = 1, b = 2;
  return;
}
int main()
{
  double n;
  scanf("%lf", &n);
  double ex = 0, k = 1, m = 1, i = 1.0;
  f();
  do
  {
    m = m * n / i;
    k = k + m;
    i++;
  } while (fabs(m) > 1e-8);
  printf("%.4lf", k);
  return 0;
}